Button-type secondary battery

Abstract

A button-type secondary battery includes an electrode assembly including a first separator, a negative electrode, a second separator, and a positive electrode that are sequentially stacked and wound, wherein ends of the first separator and the second separator are disposed closer to a center of the wound electrode assembly than ends of the positive electrode and the negative electrode; an electrolyte; and a can in which the electrode assembly and the electrolyte are accommodated. In the electrode assembly, an expansion member is attached to at least one central end of the first separator or the second separator, and the expansion member is expanded by absorbing the electrolyte.

The invention claimed is: 
     
       1. A button-type secondary battery, comprising:
 an electrode assembly including a first separator, a negative electrode, a second separator, and a positive electrode that are sequentially stacked and wound, wherein ends of the first separator and the second separator are disposed closer to a center of the wound electrode assembly than ends of the positive electrode and the negative electrode; 
 an electrolyte; and 
 a can in which the electrode assembly and the electrolyte are accommodated, 
 wherein, in the electrode assembly, an expansion member includes a first expansion member portion that is attached to at least one central end of the first separator or the second separator, and the expansion member is expanded by absorbing the electrolyte, 
 wherein each of the first and second separators has a width greater than that of each of the negative electrode and the positive electrode and is wound in a state of being stacked to protrude to both sides of each of the negative electrode and the positive electrode, and 
 wherein the expansion member further includes a second expansion member that is additionally attached to each of portions of both the sides of the first and second separators, which protrude from the negative electrode and the positive electrode. 
 
     
     
       2. The button-type secondary battery of  claim 1 , wherein a hole is formed in a center of the electrode assembly, and the expansion member is filled into the hole formed in the center. 
     
     
       3. The button-type secondary battery of  claim 1 , wherein the expansion member is attached to all the ends of each of the first separator and the second separator. 
     
     
       4. The button-type secondary battery of  claim 3 , wherein the expansion member is attached to an entire side along a width direction at the ends of each of the first separator and the second separator. 
     
     
       5. The button-type secondary battery of  claim 1 , wherein the expansion member additionally attached to each of the portions of both the sides of the first and second separators, which protrude from the negative electrode and the positive electrode, are attached to all of the both sides of each of the first and second separators. 
     
     
       6. The button-type secondary battery of  claim 1 , wherein the expansion member additionally attached to both the sides of each of the first and second separators is continuously attached along a longitudinal direction of the first and second separators. 
     
     
       7. The button-type secondary battery of  claim 1 , wherein the expansion member additionally attached to both the sides of each of the first and second separators is discontinuously attached to form a disconnected portion in a longitudinal direction of the first and second separators. 
     
     
       8. The button-type secondary battery of  claim 1 , wherein the can comprises a lower can having an opened upper side so that the electrode assembly and the electrolyte are mounted, and an upper can coupled to close the opened upper side of the lower can, and
 when the expansion member additionally attached to both the sides of each of the first and second separators absorbs the electrolyte, in the electrode assembly mounted in the lower can, both the sides of the first and second separators are spaced apart from inner surfaces of the upper can and the lower can, respectively. 
 
     
     
       9. The button-type secondary battery of  claim 8 , wherein, when the expansion member additionally attached to both the sides of each of the first and second separators absorbs the electrolyte, the expansion member disposed at a lower side of the electrode assembly and the expansion member disposed at an upper side of the electrode assembly are in contact with the inner surface of the lower can and the inner surface of the upper can, respectively. 
     
     
       10. The button-type secondary battery of  claim 1 , wherein the expansion member additionally attached to each of both the sides of the first and second separators and the expansion member attached to the central end of each of the first and second separators include a same material. 
     
     
       11. The button-type secondary battery of  claim 10 , wherein the expansion member additionally attached to each of both the sides of the first and second separators and the expansion member attached to the central end of each of the first and second separators comprise swelling tapes of the same material. 
     
     
       12. A secondary battery module, in which a plurality of button-type secondary batteries of  claim 1  are electrically connected to each other in parallel or in series.